Alliance
by Perfectsyco
Summary: Years after Merlin's attempt at killing Morgana, war rages on. He didn't think he could see anything worse than the aftermath of a battle. That is, until a new enemy shows itself.
1. Chapter 1

Title: Alliance.

Summary: Years after Merlin's attempt at killing Morgana, war rages on. He didn't think he could see anything worse than the aftermath of a battle. That is, until a new enemy shows itself.

Disclaimer: Merlin belongs to it's respective owners, of which I am not one, and no money is being made out of this.

Rating: 18/M. This is not for kids. Lots of death, probably lots a blood, and a dash of potentially explicit sex.

Pairing: Arthur/Gwen, Merlin/Morgana (but not for a while).

Note: Written because I got curious as to what would happen if Merlin and Morgana were forced to work together _after_ she had turned to evil. If this story goes as I have planned, then I will be screwing with one of the most well known legends ever for my own amusement. And yours.

This chapter is short, a sort of summery of what's happened over the years. Chapter two is longer, and nearly finished, so expect it in a few days.

Criticism welcome, either of the story or if you see spelling/grammar mistakes (although I'm pretty good there, but I'll correct if I've got something wrong). Flames, if you find it that bad, will be met with amusement on my part.

* * *

It had taken six years before the trouble really began. Six years after Morgana disappeared. Six years after a great dragon had been slain during its attempt to siege Camelot. Morgana hadn't been seen or even heard of since her disappearance. Neither had the druid boy, Mordred, or Morgause, Morgana's half sister. If Merlin had known the reason why, known that Mordred and Morgause were steadily poisoning Morgana's heart with hatred, he would have done anything to find her. Instead he stayed by Arthur's side, protecting him when needed.

Uther had passed away. An unknown sickness had slowly ate away at his health. Gaius did all he could, but eventually the only treatment he could give was to lessen Uther's pain during his final days. Merlin refused to use magic to save him, knowing that Uther's death would be natural. Merlin wasn't even sure if he'd wanted anyway.

It was shortly after Arthur's crowning that the rumours began. Whispers of an army raising, preparing to strike Camelot. None seemed to know where this army was supposed to be, who was leading it, or how large the army was. As a result, Arthur ignored the rumours, believing them to be false. He would later consider his lack of action to be his greatest mistake.

It wasn't long before the first survivor came to the castle. He was badly wounded, and survived only long enough to deliver his message. His village had been attacked by people using magic and steel in equal measure. Arthur immediately sent some of his knights to go to the village and check for more survivors.

When they returned, they looked ill. The attack had been brutal. There were no other survivors. Only one building remained standing, and only because it was the one chosen for a different purpose. The people of the village had been nailed to it. According to the knights, it didn't look as if their deaths had been quick.

No other survivors came, but reports certainly did. People would see smoke raising from a neighbouring village. They would think that perhaps a fire had gotten out of control, and would go to see if they needed help. They would find the village burned and it's inhabitants dead. Their own village would suffer a similar fate soon after.

Arthur, unable to stand by while his people suffered, amassed the armies of Camelot, with himself at their head. It was of a considerable size, and they marched throughout the kingdom, passing through the burned villages, looking for any trace of those that destroyed them. Merlin rode by Arthur's side, and Arthur would not realise exactly why he had brought Merlin with his army. Not until their first battle.

Such a battle came. They came across the enemy in the far north of a the kingdom. Arthur was shocked, and Merlin guilt ridden, to find Morgana standing alongside a teenage boy at the head of an army. Morgana had smiled at their looks, even across the field they could tell, and ordered their sorcerers to unleash their most destructive spells they knew.

None were more shocked than Arthur when his manservant conjured a magical shield around Camelot's entire army, completely impervious to the spells coming in. Mordred's army knew of Merlin's ability to do magic, but they hadn't realised how powerful he was. They soon did, as Merlin began to unleash his own spells. Bolts of energy that would kill anyone within a wide radius. Merlin made sure not to hit the woman stood by their leader, he didn't want to kill someone who he had once called a friend. But the effect on their soldiers was devastating.

Arthur, deciding that they had an advantage, charged. Between Merlin's magic and Arthur's warriors, the battle was over quickly. Soon Mordred and Morgana, with one final glare at Merlin and Arthur, led what was left of their forces into the forest. Arthur had tried to pursue them, but they hid themselves well.

Arthur had lifted the ban on magic shortly after. Seeing Merlin with such power, realising how many times Merlin could have killed him, but didn't, finally convinced the king that magic was not necessarily evil. Merlin had been appointed Court Sorcerer, and was the highest authority, answering only to Arthur, when it came to governing magic. He taught it to others, and was a good and well respected teacher. It had been a good arrangement, one which lasted for a year, until something disrupted it.

Merlin's mother, Hunith, entered the castle. Ealdor had been attacked and destroyed, with her as the only survivor. That wasn't for long though. Morgana and Mordred had done this to get revenge on Merlin, he and Arthur both knew this. Hunith had a slow working poison in her system, and she had died with Merlin at her bed side. It had not been quick, and even Gaius couldn't relieve her of the agonising pain wrought by the poison.

Merlin's rage had been terrible to behold. Arthur and Gaius watched Merlin leave the city walls on a horse with a lightning storm following him. His eyes were glowing, but not the gold colour that they normally did. His were glowing a deep red, and it made the usually gentle boy a truly terrifying site. Cloaked in black he left the city walls, and was never heard of again. For a while.

Soon whispers began amongst the druids. Fearful warnings of the warlock Emrys. A man who could call down fire from the sky, shake the very earth, and send entire armies fleeing, or dying, before him. Only one had managed to survive his onslaught, Morgana. Their friendship was long forgotten, and the only reason she survived is because her power almost matched his.

He returned to Camelot after several months, his rage subsided, or at least under control, and his eyes back to normal.. Begging Arthur's forgiveness and telling them how Mordred was still amassing forces despite all Merlin had done. Arthur had welcomed him with open arms, stating that there was nothing to forgive. Gaius hadn't let him off so lightly. Arthur had then introduced him to his new queen, Gwen. Merlin had been ecstatic for the couple, but it was soon dampened as more attacks began.

Over several months, Arthur and Merlin hardly spent any time at all in Camelot. Arthur had left the running of the kingdom to Gwen, and she had done so grudgingly, but with understanding. Mordred had amassed a considerable army, and skirmishes happened frequently. Arthur hated to admit it, but the outcome of larger battles rested almost entirely on whether Merlin would exhaust himself first, or Morgana. Their armies were evenly matched, Camelot's swords and bows were superior, but Mordred's army held the greater amount of sorcerers. Merlin was the most powerful sorcerer, but Morgana was a seer. Arthur was by far the best swordsman, but Mordred had enhanced his own body, sacrificing his magic to do so. Battles would be fought around Merlin and Morgana, with only a very select few daring to help either of them. They would rarely survive. Neither Merlin nor Morgana were able to finish the other off, it had become common practice for their allies to retreat as soon as their battle was over, with the loosing side getting their sorcerer out of there using magic.

When Merlin killed Morgause, bad blood was a pitiful understatement of the hatred between him and Morgana. The first thing they would do on the battlefield would be to find each other, and their battles became so brutal that none would dare to interfere, knowing full well that they would be killed instantly. Arthur and Mordred, too, sought each other on the battle field. Their fights were no less vicious, but less damaging to those around them.

But neither side new of a new enemy in the making. A group of druid sorcerers had isolated themselves from the fighting. They resented both Arthur for killing so many of their people, and Mordred for putting those people in a position to be killed. They experimented with magic, until one of them came across a book. Filled with spells more evil and powerful than they had ever seen, they were corrupted absolutely. A few would hear dark rumours of what their experiments became. Those few would soon become a part of those experiments.

Mordred and Arthur would both remain ignorant about this new evil brewing. Growing in their power while those they wished to destroy were too busy with each other to notice anything else. It wasn't until a would-be final battle that they found out.


	2. Chapter 2

Chapter two: the enemy of my enemy is most certainly _not_ my friend.

* * *

A vast field separated the two large armies. Merlin took a moment to take in it's simple beauty; lush green grass and the occasional wild flower. Even with the sky overcast it looked beautiful. He knew with regret that it would not be that way for long. Soon it would be no more than a bloody wasteland. Even the outlining forest may not survive. It was something he was all too familiar with.

He stood next to Arthur, who was clad in heavy plate armour. How the man managed to move and fight with his level of fluidity in that armour was beyond Merlin. At his hip was Excalibur. On his left arm was a large shield, Camelot's coat of arms displayed proudly on the front of it. Arthur's face was as handsome as ever, although harder than it used to be. Merlin knew that the same couldn't be said about his arms. His elbows down to his wrist, on both arms, were covered in scars from the times when a blade had pierced his armour. Most of these were caused by Mordred.

Merlin himself wore no armour, and carried no sword. He wore a simple black cloak. A very select few would still consider this to be the height of stupidity. But anyone who had seen him in battle knew one simple truth; Merlin did not need armour. Still, Merlin was not unscathed. The only scar on his face was small, and ran down his left cheek. Under his clothes, on his torso, was a scar that was obviously a burn. A particularly nasty enchantment cast by Morgana had torn through his magical shield and hit him directly. She had won that battle, as he had won so many others. Merlin used to carry a staff, as did Morgana, but their power and control had gone beyond the need for them. They rarely even needed incantations now.

Behind them the men stood proudly, happy to serve under their king even if it meant their own deaths. It was one key difference between Arthur's reign and Uther's. Under Uther the men had served him simply because it was their job to do so. But Arthur was well loved by all of his people, they served him because they wanted to. Merlin was proud of what his best friend had become. Looking over the field, he thought it was a shame that another one time friend hadn't gone the same way.

Noise was heard over the field as rain began to fall, Mordred's forces were cheering. This was it, this would be the end of a three week calm. By unspoken agreement, both sides had decided that this had to end, and not a moment too soon. There had been so much death, so many loved ones lost that both sides had wanted this over with. So the skirmishes had stopped, as had the attempts at infiltration and assassination. Merlin himself had passed a group of enemy soldiers without attacking. They were simply giving each other time to rest and muster their forces before this battle began. That calm would be shattered today.

"Merlin? Are you ready to end this?" Arthur asked.

"I've been ready for a while now, Arthur," Merlin replied with a grim smile.

"Really?" Arthur said, incredulity lacing his tone as they slipped into familiar teasing. "Then why is that witch still alive?"

Merlin smiled, if it were anyone else he would have been deeply offended. "Because I think she's pretty."

"That's no excuse," Arthur shot back.

"So what's yours? You can't say Mordred is pretty. Unless there's something you want to tell me."

A few of the men chuckled behind them, those who had served under Arthur before knew this teasing well.

"You may be Court Sorcerer now but I can still have you put in the stocks," Arthur said in a mock warning.

"So there is?" Merlin tutted. "Gwen is going to be angry."

"That's Her Majesty to you, Merlin."

"If I carry on trying to call her that then _she_ will put me in the stocks," Merlin replied.

The two friends smiled, one thinking of a lover, the other thinking of a sister. They silently promised themselves that they would return to her. They were drawn from their thoughts as the cheering from the other side of the field grew louder.

Arthur's face grew serious as he drew his blade, and Merlin heard the distinct sound of soldiers doing the same behind him. Archers were loading their bows, sorcerers were bringing their most brutal spells to the forefront of their minds. Merlin looked over the field to the dark haired woman in the green cloak, and he was sure that she was looking back at him. It was almost tradition now. Even with the rain coming down in torrents, he could see her clearly. Briefly looking at Arthur, he knew that his eyes had found Mordred, the teenage boy with unnatural talents in close combat.

Arthur had his shield in front of him and his legs bent, ready to charge at a moments notice. Merlin and most of the other soldiers were in a similar position. Merlin found himself fleetingly wondering who would charge first.

"Merlin!" Arthur' voice called, tearing him from his thoughts.

Following his line of sight, Merlin found the reason for the kings distress. What looked like a line of orange light had appeared before Mordred's forces, and was shooting toward Camelot's army with alarming speed. Understanding what was happening, and wondering why it was happening, Merlin stretched his hand forward, and his eyes shined gold as the air around them seemed to shimmer slightly.

Arthur and the rest of men only had a brief time in which to realise that the light was not a line, just a huge number of balls of fiery orange light. They slammed into the shield with unrelenting force, causing it to become visible; stretching and straining under the onslaught, but holding.

Merlin let the shield drop as soon as it was over. He had no idea why they had tried that, when they knew very well that it wouldn't work. He had little time to wonder, as it soon became clear. Mordred's forces were charging, the magical attack had been nothing more than a distraction.

A flash of lightning, a thundering war cry, and they were charging too. Arthur was heading straight for Mordred, and Merlin for Morgana. He briefly let himself notice of the arrows flying overhead, the spells shooting past his head but never hitting. He knew that a lot of people were dying already, but he couldn't think about it as Morgana got close enough to fire the first spell.

It was powerful, and almost staggered Merlin with the force it took to block it, but Merlin was soon retaliating with a powerful jet of fire. The wind whipped up around them, marking an area that none would dare step into. They entered a dance that they had performed many times. Spells flew between them, tearing and scorching the ground around them as they were deflected and blocked. Merlin called forth a spirit of fire, the flaming head of a wolf lashing out towards Morgana, bouncing off her shield, and then battering it again. It would never breach her shield, but would hopefully distract her. Morgana was using the earth to a similar diversionary effect, casting enchantments to make the grass grow long and tie around Merlin's legs. The earth around them trembled as they poured more and more power into their spells. It was now a question of who would make the first mistake.

--

Unseen by the armies before it, hidden by the tree line, it watched. It watched and smiled as the two armies killed each other. Soldiers were dropping left and right, succumbing to blades and spells alike. Neither were using arrows any longer, the armies were so intermingled that they would hit their own forces.

The pale, almost white figure in a black cloak said something in a whisper that chilled everything around them. The plants around it began to die as it spoke, as if the figure were sucking the very life from them. The forest around it grew unnaturally dark, and any animal life found itself running as if the greatest of hunters were chasing them.

Behind the figure, another came into view. It wore dull metal armour and carried a huge two handed sword. It was a tall and well built figure, looking almost human. Its face was pale, its eyes seemed to be made of obsidian. It snarled something in an unknown language, it's voice deep and monstrous. Heeding it's call, another came up beside it. And another, and another. The forest was soon filled with these pale warriors, and their obsidian eyes were all fixated on the battlefield in front of them.

--

Thrust. Block. Parry. Swipe. Parry. Arthur was used to sword fights, he had been training with swords his whole life. But never had he felt the impacts like this. Whatever Mordred had done, the teenager's strength was vastly superior to his own, and every time their swords clashed he felt it right through to his bones. But luckily he lacked Arthur's finesse. This was proven as Arthur ducked under a powerful swipe intended to take his head off, and followed up by ramming his shield into Mordred's face, momentarily staggering him. Their swords clashed again as Mordred quickly recovered, and they pushed against each other with all their might. They knew in their hearts that they would finish this today. But they were wrong.

Something slammed into them both from the side, with enough force to send them both to the ground. They got up as quickly as they could, each looking around for someone who they thought was helping their opponent. But it was a body, one of Camelot's soldiers, and he had been slashed wide open with enough force to send him flying.

As the two enemies looked towards the direction that the body had come from, their eyes widened in shock.

--

Merlin pushed all of his power through his hands. Raw, destructive magical energy roaring out, and slamming into Morgana's own causing a maelstrom of brilliant white energy between them. Both were locked in place, hands stretched before them as their magic pushed against each other. The ground in between them was cracking, as if the earth itself were trying to separate them before they did any more damage. Merlin was getting tired, he had never poured so much energy out in such a short time. Not even in the other battles with her.

"Merlin!"

He heard Arthur's voice, but faintly, and didn't stop.

Morgana smirked evilly, it still looked almost out of place on her once gentle face.

"Looks like your master needs you, Merlin," she sneered, but from the strain in her voice, she was in no better condition than he was.

"Friend, actually," Merlin shot back through gritted teeth. "Do you remember what it's like to have one?"

Her reply was cut short as another voice cut through the noise.

"Morgana!"

It was Mordred.

Both extended their senses a little, trying to find out what was happening without taking too much attention off each other. Both became confused as they realised that soldiers from both sides were charging in the same direction, seemingly toward the same objective, and yet they weren't fighting each other.

They locked eyes, silently agreeing to a momentary truce while they found out what was going on.

When the energies stopped they both almost fell forward, the sudden pressure against them dissipating in an instant. The winds whipping around them ceased, the sound dropping to a volume that allowed them to hear the clashing of metal and the screams of men.

Running towards the sound, they saw what was happening straight away. An army of warriors, pale and hulking, were emerging from the trees and attacking everyone in sight. Both considered briefly that the other was responsible for it, but it was obvious that these new warriors were indiscriminate in their slaughter.

"Arthur?" Merlin asked, standing next to the king, briefly seeing Morgana get to Mordred a short distance away. "What's happening?"

"I don't know," Arthur said, his eyes surveying the bloodbath before him.

Merlin watched as another soldier fell, wincing as one of the pale warriors cut the poor man clean in half. Whoever these new warriors were, they were obviously winning. Looking at their pale faces and obsidian eyes, Merlin knew very well that they were not natural, or human.

Arthur looked to Mordred, who stared back with his alarmingly blue eyes. Both nodded, almost imperceptibly, before shouting the orders for their forces to retreat.

"Merlin, do you think you can slow them down enough for us to escape?" Arthur asked.

"Yes," Merlin said, a dark smile on his lips.

He looked towards his new enemy. They had formed a long, straight line, and were slowly but steadily marching in perfect synchronisation towards the retreating soldiers. They still had a few minutes until they were within a swords reach of themselves, but the same couldn't be said for some of the soldiers. Merlin shot his hand forward and a blue bolt of energy shot out. It took more effort than it usually would thanks to his battle with Morgana.

The bolt struck one of the pale warriors directly, and the resulting explosion brought down the three next to it in both directions. Arthur smiled grimly, he had seen Merlin use that one many times.

But then something happened that neither Merlin nor Arthur had seen before. The warriors picked themselves up from the ground, caught up with their brethren, and continued their relentless march. Completely unharmed, not even a dent in their armour.

Merlin was shocked, knowing full well that his spell should have killed them. Even as drained as he was, that bolt had held enough power to kill a group of soldiers from the impact of the blast alone.

Any _human_ soldier, he thought to himself. Looking to Morgana he saw that she too had a frown on her face. She looked back at him, and he inclined his head once, indicating that she should try. She scowled, hatred in her eyes, but did so none the less.

At the same time, they both unleashed one of the more wide spread fire spells that they knew. Merlin's hit toward the right of the line of warriors, while Morgana's went toward the left. The ensuing fire, despite the rain, was both frighting and surprising in it's intensity, even to the two who had cast them; it had been a long time since either of them had used such destructive spells on anyone but each other.

The grass set alight, the pale warriors set alight, but they marched on. The blazing fires, unhindered by the downpour, reached far past even the warriors large height, yet their faces remained unblemished. Their march continued, getting too close now. The last of the soldiers had managed to pass them. Now all that stood between the warriors and themselves were the bodies of those that had already died.

It was then that they decided to follow in the footsteps of their soldiers.

Merlin decided on one last course of action before he turned and fled. He cast a spell, similar to the shield spell he had used on Camelot's army earlier. It took it's toll on him, he felt almost ready to collapse. The shield shimmered into existence before the line of marching warriors, and it stretched and strained as they tried to march right through it. Merlin fearfully realised that it was not going to hold this time.

Out of nowhere the shield suddenly solidified and snapped back, pushing the warriors back with considerable force. Merlin turned to see Morgana, hand outstretched, reinforcing the shield herself. It seemed that they agreed on something, possibly for the first time in years.

"Come on," Merlin said to Arthur, who's grief filled eyes were surveying the field, filled with the bodies of many of his soldiers. "We need to leave, it won't hold forever."

Merlin was proven right, as even with Morgana's reinforcement the shield was still stretching, albeit a lot more slowly than it was before.

Arthur nodded once, and they turned and ran, jumping and stepping over bodies and dropped weapons. Vaguely they were aware of Mordred and Morgana doing the same, but lost sight of them as the four of them entered the tree line on the opposite side of the field from the warriors. Merlin turned back once, and what he saw chilled him. The warriors had stopped trying to march through the shield. In front of them and the shield stood a black cloaked figure, it's hands stretched toward it. Merlin couldn't explain it, but he felt more afraid of this figure than anyone he had ever met in his life.

--

Night had fallen by the time they caught up with what was left of Camelot's army. Arthur was shocked to see how few had survived. A few hundred, out of the many, many more that had marched behind him just this morning. They looked confused, and a little afraid, no doubt wondering who this new enemy was.

Neither Arthur nor Merlin spoke a word as they passed the injured men, each wondering the same thing and contemplating possibilities. Who were those warriors? Where had they come from? Who was leading them? Most importantly, how had they not known about an enemy so powerful?

They sat down in front of a fire. There were no tents set up, those who could sleep were doing so sitting on the ground, back to back so their heads wouldn't rest on soil. Some were keeping a look out, patrolling around the perimeter of the camp. They weren't sure what they would do if the pale warriors found them, but they knew they would at least warn their comrades.

Arthur and Merlin both took a flask of mead offered to them by two of the men. All of the men had one, it was something to celebrate victory with, if they were victorious. Now it was simply comforting.

"What were those things Merlin?" Arthur asked, the dancing fire illuminating his features.

"I don't know," Merlin admitted, an usual thing these last few years. "I know they weren't human, but that's all. I don't even know who it was that was leading then."

"We never saw a leader," Arthur agreed, only to see Merlin frown briefly. "Did we?"

"I don't know. While we were running away-"

"Strategically retreating."

"-I saw someone in a cloak trying to dispel the shield I cast, and that Morgana reinforced. I don't know if it was their leader or just another one of their forces, but it seemed...chilling," Merlin said.

"Chilling?" Arthur asked, eyebrow raised.

Merlin nodded. "I don't know how to explain it. But when I saw it I just felt...afraid."

The few men around them shivered. They had all seen Merlin in battle, and knew very well that anything able to scare Merlin meant bad news for them.

"Okay," Arthur said. "What about their main force then? Those brutes with the huge swords. If they aren't human, then what are they?"

"I've no idea. I've never seen anything like this before. Never even heard of it."

"Do you think Gaius would?" Arthur asked.

"I hope so."

They both remained silent throughout the rest of the night. Neither slept, remembering the slaughter they had witnessed at the hands of seemingly invincible warriors. Neither admitted it, but the night seemed somehow darker.

* * *

End Chapter 2.


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